1. Field of the Invention
The present invention relates in general to data processing systems and, in particular, to a data processing system and method for efficiently determining a return current spread in a printed circuit board. Still more particularly, the present invention relates to a data processing system and method for efficiently determining a return current spread at an evaluation point in a printed circuit board by adding the return current due to each one of a plurality of critical traces.
2. Description of the Related Art
Microstrip and stripline return currents in printed circuit board reference planes will spread across the reference plane and cause EMI emissions. These EMI emissions increase when external connectors or wires are attached to the board, such as when a keyboard or mouse are connected, or for wires carrying audio signals.
When a printed circuit board is designed, each trace to be included on the board is laid-out in one of the possible trace positions on the board. An engineer laying-out the board must rely on education and experience in selecting the best lay-out of the traces for the board.
Personal computer systems are well known in the art. They have attained widespread use for providing computer power to many segments of today""s modern society. Personal computers (PCs) may be defined as a desktop, floor standing, or portable microcomputer that includes a system unit having a central processing unit (CPU) and associated volatile and non-volatile memory, including random access memory (RAM) and basic input/output system read only memory (BIOS ROM), a system monitor, a keyboard, one or more flexible diskette drives, a CD-ROM drive, a fixed disk storage drive (also known as a xe2x80x9chard drivexe2x80x9d), a pointing device such as a mouse, and an optional network interface adapter. One of the distinguishing characteristics of these systems is the use of a motherboard or system planar to electrically connect these components together. Examples of such personal computer systems are IBM""s PC 300 series, Aptiva series, and Intellistation series.
Currently computers are utilized in the design and lay-out of printed circuit boards. For example, theoretically, full-wave modeling may be utilized to find the currents everywhere on the reference plane due to all of the various traces. However, it is impractical, if not impossible to perform full-wave modeling for each potential circuit board design to determine the total return current spread at each possible evaluation point on the reference plane.
Therefore a need exists for a data processing system and method for efficiently determining a total return current spread at any evaluation point in a reference plane in a printed circuit board.
A data processing system and method are disclosed for efficiently determining a total return current spread at an evaluation point in a reference plane in a printed circuit board. A plurality of critical ones of a plurality of traces included within the printed circuit board are identified. For each one of the plurality of critical ones of the plurality of traces, a return current function is determined including a return current value produced by only each one of the plurality of critical ones of the plurality of traces at each point in the reference plane. A total return current spread is determined at the evaluation point utilizing the return current function associated with each one of the plurality of critical ones of the plurality of traces.
The above as well as additional objectives, features, and advantages of the present invention will become apparent in the following detailed written description.